This distinction seems more arbitrary over time. Growing up I was taught different species couldn’t interbreed. But what about Neanderthal and Sapiens?
Funny tangent: this comic has strong feelings about such distinctions, using "dog" as the canonical example:
I don't think you could have chosen a worse example. Dogs are themselves a subspecies, and are split into many different breeds, of wildly different character and physiology: https://en.wikipedia.org/wiki/Dog#Taxonomy
Breeds and species are different things. Parent post is making a (very good) point that dogs can pretty much all breed with one another.